1. Field of the Invention
The present invention relates to missile control systems, and particularly relates to a thrust vector control for jet tab actuators coupled to an aerodynamic control system employing a geared summing mechanism.
2. Description of the Prior Art
It is known in the art to provide jet tabs for controlling the thrust vector. The jet tabs are movable into the rocket exhaust stream for controlling the flight path of a jet or rocket-driven vehicle, such as a missile. Such a system serves to enhance or supplement the attitude control usually provided by aerodynamic control surfaces.
When a rocket vehicle, such as a missile, is launched from the earth, the initial flight is at relatively low speeds. During this portion of the flight the aerodynamic control surfaces of the missile are less effective than during later periods of the flight where the speed is much higher. Hence, during a typical, low-speed launch period, thrust vector control may be effective to augment pitch and yaw control.
While the vehicle travels at certain altitudes and speeds, significant aerodynamic effects may be obtained by the control surfaces. In that case, thrust vector control may not be necessary. However, at higher altitudes, the aerodynamic effects are reduced due to low atmospheric density. In this case, pitch and yaw attitude control may be enhanced again or may only be available by thrust vector control.
Jet tabs for thrust vector control are inserted into the missile exhaust flow where they deflect the exhaust gases. This, of course, provides control moments. Such jet tabs are effective for providing pitch and yaw attitude control. However, they are ineffective to provide roll control. Hence for roll control, reliance is usually placed on aerodynamic surfaces or on different types of thrust vector control, such as separate jets having an exhaust flow forming an angle with the longitudinal axis of the vehicle.
Conventional thrust vector control by tab actuator systems generally employ power actuators which are independent of the actuators for the movable aerodynamic surfaces. In such prior systems, pitch, roll and yaw commands are provided to the aerodynamic control surface actuators. On the other hand, only pitch and yaw commands are provided to the thrust vector control of the jet tabs. Hence, two separate sets of commands and two separate sets of actuators are required, thus increasing the weight and complexity of the missile.
Devices which may generally be categorized as geared summing mechanisms have been employed in machines of various kinds. Here a number of inputs are added algebraically to provide a summed output. Examples of such machines are found in the patent to Dietrich et al. U.S. Pat. No. 2,942,496 and Weiland, U.S. Pat. No. 3,457,806.
Other relevant prior art is found in the patent to Geissler et al, U.S. Pat. No. 3,139,033, entitled "Aerodynamically Stable Missile." The missile disclosed in the patent includes jet vanes disposed in the exhaust flow. They are mechanically connected to air fins for simultaneous movement. According to this patent, pitch, yaw and roll commands sent to the air vanes are merely transmitted to the jet vanes.